Coordination framework materials fabricated by the self-assembly of Sn(iv) porphyrins with Ag(i) ions for the photocatalytic degradation of organic dyes in wastewater

Abstract

Two porphyrin-based coordination frameworks, [Ag₂(TPyP)Sn(OH)₂](NO₃)₂·(solv)_x (1) and [Ag₂(TPyP)Sn(INA)₂](OTf)₂·(CH₃CN)₂ (2) (INA = isonicotinato anion, OTf = CF₃SO₃⁻), were constructed by the self-assembly of hexacoordinated (meso-tetra-(4-pyridyl)porphyrinato)Sn(IV) building blocks with Ag(I) ions. They were characterized using elemental analysis, UV-visible spectroscopy, fluorescence spectroscopy, FT-IR, field-emission scanning electron microscopy, and X-ray crystallography. The structural motifs of the framework materials vary from 2D to 3D, depending upon the axial ligation of the Sn(IV) porphyrin centers. Their photocatalytic performance was also investigated for the degradation of cationic methylene blue (MB), anionic amaranth dye (AM), and neutral bromocresol green (BCG) dyes in aqueous solutions under visible-light irradiation. The photocatalytic efficiency of 2 was higher than that of 1. The pseudo-first-order rate constants for the degradation of dyes by 1 were estimated to be 0.015 min⁻¹ (MB), 0.021 min⁻¹ (AM), and 0.009 min⁻¹ (BCG). In the case of 2, they were 0.020 min⁻¹ (MB), 0.031 min⁻¹ (AM), and 0.011 min⁻¹ (BCG).